Spectral line estimation using complex coefficient prefilters

A spectral line estimation method is proposed which improves the resolution of the two nearby sinusoidal frequencies. In contrast to the conventional method in which the decimation operation is applied to the signal passing through the real coefficient bandpass prefilter, the present method carries out the process by means of the complex coefficient prefilter. By means of this technique, numerous problems to be resolved under the condition that relatively few data are given under a low SN ratio, such as the problem of initial phase dependence and the problem of accurate spectral estimation at a low- or high-frequency region, can be overcome. This paper presents a method in which the decimated signals by a decimation operation are used effectively. The method particularly improves the estimation capability in the case with fewer data. Finally, by means of a simulation, the effectiveness of these methods is proven. It is shown that the estimation accuracy is improved significantly as long as the amount of operations is similar to that for the conventional method using the real coefficient prefilter.